The present invention relates to a system and a method of thermal conditioning as a continuous process of a fluid sample, more particularly of an oil drilling mud
During the drilling of an oil well, a fluid known as drilling mud is made to circulate inside the hole while drilling. The drilling mud has various functions including, in particular, those of: supporting the drilled hole, lubricating and cooling the auger while drilling of the well. The drilling mud has, moreover, the function of conveying rock fragments to the surface produced while drilling. The rock fragments are produced by the mechanical impact of the drill bit traversing the rocky layer, resulting in drilling debris and volatile substances released during the break-up action.
Among fluids and gaseous components, liquid and gaseous hydrocarbons are of particular importance because they are indicators of the existence of an oil or gas deposit.
The gaseous fraction contained in the drilling mud conveyed to the surface is commonly extracted by means of an apparatus known as degasser, after which it is diluted in a carrier gas, generally air, and finally transferred to various analysis apparatuses able to identify the quality and quantity of various components of hydrocarbons present. The degasser is continuously fed by a volumetric pump which samples the fluid to be degassed at the point closest to the well exit.
In certain working conditions, in particular in the drilling of wells in deep waters (from 1000 to 3000 metres of water), the drilling mud must upwardly traverse a column of water of considerable height, cooling progressively, before reaching the point of sampling. Due to this cooling, the drilling mud that reaches the degasser has a temperature often below 10° C. Such a temperature entails considerable difficulties in extracting and analyzing the hydrocarbons present.
Also, in these conditions, the rise of mud is at times aided by a supplementary pump that injects drilling mud already degassed into a circuit rising from the seabed, in this way diluting the mud coming from the well and consequently the gaseous fraction contained therein. This considerably reduces the percentage of hydrocarbons present in unit of volume, making their extraction and quantification additionally difficult.
For these reasons, the hydrocarbons brought to the surface may be in extremely low concentrations (and in two-phase gas/liquid equilibrium), conditions which as a whole make the subsequent process of extraction and analysis in gaseous phase very difficult.
It is therefore necessary to thermally, i.e. heat, condition the drilling mud so as to facilitate the extraction of the hydrocarbons thereby improving the precision and resolution of their subsequent analysis.
The systems for thermal conditioning of drilling mud currently present on the market are essentially electric heating systems that use plate heat exchangers. These systems, however, have various disadvantages, including the length of time interval required for raising the temperature of the drilling mud, which consequently delays the sending of the gas sample for subsequent qualitative and quantitative hydrocarbon analysis. This delay may be particularly hazardous in light of the particular risks involved in handling certain gases.